Copper alloys which are used extensively in plumbing products such as brass fittings generally exhibit poor machining characteristics. To improve the machinability of these alloys lead has been added to the composition.
Recently, attention has focused on the possible leaching out of lead into water resulting in a health hazard. Because of this deleterious effect of lead in potable water it has become desirable to eliminate lead from these brass products that come in contact with drinking water. In addition to the toxic contamination of water by lead the machining of these brass fittings leads to toxic waste.
Research has been conducted to produce copper graphite composites using powder metallurgy techniques to produce samples for machinability. In addition a process covered by U.S. Pat. No. 4,207,096 teaches a method of casting permitting an uniform dispersion of graphite in copper. This novel casting technique as covered by U.S. Pat. No. 4,207,096 apparently avoids the inherent difficulty in evenly dispersing graphite in a copper or another material matrix. These difficulties are due mainly to the differences in specific gravity of the dispersing material and the matrix causing float up and uneven dispersion. Another difficulty of obtaining an homogeneous composite is due to the soluble incompatibility of the two materials.
Research conducted in the field of copper graphite composites during the past fifteen years indicates mainly an effort directed to producing composites with tailored friction or expansion or damping properties.
The present invention resulted from research effort focusing on the improvement of the machinability of copper alloys through the use of a simple casting process to produce copper graphite particle composites with machinability characteristics similar to leaded copper alloys.